Abstract 16230: Genetically Confirmed Hypertrophic Cardiomyopathy, Initially Misdiagnosed as Cardiac Amyloidosis by Cardiac Biopsy

Abstract

A 72-year-old male was admitted with worsening dyspnea. 5 years ago, echocardiography demonstrated biventricular hypertrophy with highly reflective myocardium. Cardiac MRI demonstrated epicardial and mesocardial late gadolinium enhancement suggesting possibility of infiltrative cardiomyopathy. Endomyocardial biopsy revealed the deposition of eosinophilic amorphous material, consistent with amyloidosis. Congo red stain was also compatible with cardiac amyloidosis. There was no evidence of monoclonal gammopathy in the serum and urine immunofixation and electrophoresis. He was diagnosed with cardiac amyloidosis of unknown etiology. 2 years later, he complained dyspnea on exertion. Echocardiography revealed decreased LV systolic function (LVEF 53 -> 38%). Single gene mutation test for TTR and a-galactosidase level turned out to be negative. Recently, echocardiography seems to be more stiff and accompanied by slight wall thinning locally. Cardiac MRI demonstrated wall thickening has been slightly decreased and enhancement of interventricular septum appeared to be more prominent. We performed DPD bone scan and it showed no cardiac uptake, suggesting low probability of ATTR cardiac amyloidosis. We performed genetic test (whole exome sequencing based on next generation sequencing) and it showed MYBPC3 (myosin binding protein C3) gene mutation, which suggestive of hypertrophic cardiomyopathy. He was discharged with heart failure medications and familial screening is in progress. HCMP can be presented with many faces which often hampers the true diagnosis. We often think of pathological findings as a golden diagnosis, and try to match everything to the pathological findings, but cardiac pathology is a relatively unfamiliar area for most pathologists. Cardiologists need to closely review clinical and imaging findings along with pathological findings. And additional testing, such as genetic testing, may be helpful in making a diagnosis.